Regional police said three women were travelling in a car south on Highway 105 in Alcove — just north of Wakefield — when they saw the horses on the road and couldn't stop in time before hitting one of them.
The horses had escaped an enclosure police say was not properly closed.
The driver and front passenger were both transported to hospital with non-life threatening injuries, police said, while the back passenger was unhurt.
The horse was injured but is expected to survive.
The car was a total loss, police said.
The road was partially closed but reopened at about 9:30 p.m.